J/MNRAS/500/655 Galactic DM contribution to the extragalactic FRBs (Das+, 2021)
Empirical estimates of the Galactic halo contribution to the dispersion measures
of extragalactic fast radio bursts using X-ray absorption.
Das S., Mathur S., Gupta A., Nicastro F., Krongold Y.
<Mon. Not. R. Astron. Soc., 500, 655-662 (2021)>
=2021MNRAS.500..655D 2021MNRAS.500..655D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Galaxies ; QSOs ; Transient ; Radio sources ;
X-ray sources
Keywords: Galaxy: halo - quasars: absorption lines - cosmology: miscellaneous -
radio continuum: transients - X-rays: diffuse background
Abstract:
We provide an empirical list of the Galactic dispersion measure
(DMGal) contribution to the extragalactic fast radio bursts (FRBs)
along 72 sightlines. It is independent of any model of the Galaxy,
i.e. we do not assume the density of the disc or the halo, spatial
extent of the halo, baryonic mass content, or any such external
constraints to measure DMGal. We use 21-cm, UV, EUV, and X-ray data
to account for different phases, and find that DMGal is dominated by
the hot phase probed by X-ray absorption. We improve upon the
measurements of N(OVII) and fOVII compared to previous studies, thus
providing a better estimate of the hot phase contribution. The median
DMGal=64+20-23cm-3pc, with a 68 per cent (90 per cent)
confidence interval of 33-172(23-660)cm-3pc. The DMGal does not
appear to follow any trend with the Galactic longitude or latitude,
and there is a large scatter around the values predicted by simple
disc + spherical halo models. Our measurements provide more complete
and accurate estimates of DMGal independent from the previous
studies. We provide a table and a code to retrieve DMGal for any FRB
localized in the sky.
Description:
Based on 21-cm, UV, and X-ray absorption analyses at z=0 along 72
sightlines, we provide an empirical list of the Galactic dispersion
measure (DM) contribution to the extragalactic fast radio bursts
(FRBs). It is independent of any density model and the spatial extent
of the Galactic halo. We improve upon the measurements of N(OVII) and
fOVII compared to previous studies, thus providing a better estimate
of DM in the hot phase.
We tabulate the Galactic DM from the hot and the cold phases in Tables
A1, A2, and A3. We also calculate the average and maximum DM along
each sightline (see Table A4).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 61 21 DMhot based on the OVII and OVIII measurements
of Gupta et al. (2012ApJ...756L...8G 2012ApJ...756L...8G,
2017ApJ...836..243G 2017ApJ...836..243G) and DMcold based on the
21-cm measurements of HI4PI Collaboration
(2016A&A...594A.116H 2016A&A...594A.116H)
tablea2.dat 107 67 DMhot based on the OVII and OVIII measurements
of Nicastro et al. (2016) and DMcold based on
the 21-cm measurements of HI4PI Collaboration
(2016A&A...594A.116H 2016A&A...594A.116H)
tablea3.dat 55 56 DMcold and DMhot based on the ionization
modelling of Gatuzz & Churazov
(2018MNRAS.474..696G 2018MNRAS.474..696G)
tablea4.dat 100 77 Average and maximum Galactic DM, combining
multiple methods and instruments
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See also:
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Line Line used to compute DMhot
12- 22 A11 --- Name Target name
24- 29 F6.2 deg GLON Galactic longitude
31- 36 F6.2 deg GLAT Galactic latitude
38- 41 F4.2 pc/cm3 DMcold Dispersion measure of cold gas based on the
21-cm measurements of HI4PI collaboration et
al. (2016A&A...594A.116H 2016A&A...594A.116H, Cat. J/A+A/594/A116)
(G1)
43- 48 F6.2 pc/cm3 DMhot Dispersion measure of hot gas based on the
OVII and OVIII measurements of Gupta et al.
(2012ApJ...756L...8G 2012ApJ...756L...8G, 2017ApJ...836..243G 2017ApJ...836..243G)
(G2)
50- 55 F6.2 pc/cm3 e_DMhot Lower error on DMhot
57- 61 F5.2 pc/cm3 E_DMhot Upper error on DMhot
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 37 A37 --- Line Line used to compute DMhot (1)
39- 55 A17 --- Name Target name
57- 62 F6.2 deg GLON Galactic longitude
64- 69 F6.2 deg GLAT Galactic latitude
71- 75 F5.2 pc/cm3 DMcold Dispersion measure of cold gas based on the
21-cm measurements of HI4PI collaboration et
al. (2016A&A...594A.116H 2016A&A...594A.116H, Cat. J/A+A/594/A116)
(G1)
77- 80 F4.2 pc/cm3 e_DMcold Error on DMcold
82- 90 F9.2 pc/cm3 DMhot Dispersion measure of hot gas based on the
OVII and OVIII measurements of Nicastro et al.
(2016MNRAS.457..676N 2016MNRAS.457..676N) (G2)
92- 98 F7.2 pc/cm3 e_DMhot ? Lower error on DMhot
100- 107 F8.2 pc/cm3 E_DMhot ? Upper error on DMhot
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Note (1): Along some sightlines, the measurement of the OVIII line is not
reported. This is either because OVIII line was too weak to obtain a
measurement of the column, or OVIII could not be studied due to
instrumental features at that wavelength. In these cases, we assume
the ionization fraction of OVII to be equal to 1 (fOVII=1)
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Name Target name
20- 25 F6.2 deg GLON Galactic longitude
27- 32 F6.2 deg GLAT Galactic latitude
34- 38 F5.2 pc/cm3 DMcold Dispersion measure of cold gas based on the
ionization modelling of Gatuzz & Chrazov
(2018MNRAS.474..696G 2018MNRAS.474..696G) (G1)
40- 43 F4.2 pc/cm3 e_DMcold Error on DMcold
45- 49 F5.2 pc/cm3 DMhot Dispersion measure of hot gas based on the
ionization modelling of Gatuzz & Chrazov
(2018MNRAS.474..696G 2018MNRAS.474..696G) (G2)
51- 55 F5.2 pc/cm3 e_DMhot Error on DMhot
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg GLON Galactic longitude
13- 23 F11.7 deg GLAT Galactic latitude
25 A1 --- flag [*] Flag (1)
27- 39 F13.8 pc/cm3 DMavg Average dispersion measure
41- 54 F14.9 pc/cm3 e_DMavg Lower error on DMavg
56- 70 F15.9 pc/cm3 E_DMavg Upper error on DMavg
72- 85 F14.8 pc/cm3 DMmax Maximum dispersion measure
87-100 F14.9 pc/cm3 sDM Systematic uncertainty on the dispersion
measure
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Note (1): This line was commented (preceded by #) in the original table
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Global Notes:
Note (G1): Here, 'cold' refers to ∼104K gas which is predominantly neutral
Note (G2): Here, 'hot' refers to ≥106K gas probed by H- and He-like ions,
e.g. OVII and OVIII
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 18-Sep-2023